The present invention relates to a method of making a magnetic therapeutic sheet for relieving lumbar pain, nervous pain such as stiff shoulder, muscular pain, and other inflammation.
1. Field of the Invention
A prior art therapeutic sheet or compress comprises commonly a stretchable fabric coated at one side with a film of adhesive material which contains a given amount of analgesic, antiphlogistic agent. The compress is used to cover an affected area with its adhesive side by directly applying to or securing with pieces of adhesive tape.
2. Description of Related Art
It is also known that magnetic flux helps ease lumbar or shoulder pain. For this end, a disk shaped magnet, for example, 5 mm in diameter and 2 mm in thickness, is provided for placing over the affected area with a strip of adhesive tape. More commonly, a base material such as a sheet of fabric is impregnated with grains or powder of magnet as well as an adhesive agent. This application will however be disadvantageous because the magnetic powder is located at the same area as of the adhesive agent and fails to provide an intensive magnetic effect to a desired area. As the magnetic powder is distributed throughout the base material and mixed with the adhesive agent, its magnetic force is reduced at each local region thus assuring less therapeutic effects.
We have developed and proposed a number of modified magnetic therapeutic sheets capable of providing both a wet pad effect and a magnetic therapeutic effect while ensuring the magnetic effect over a wider area, as disclosed in Japanese Patent Applications 3-95152(1991) 3-95153(1991), 5-41011(1993), and 6-41011(1994).
Particularly, Application 5-41011 explains a method of making the magnetic layer through applying or printing a powder of magnetic material.
The magnetic powder is preferably a cobalt material (Sm2Co17, samarium cobalt) coated or printed on a sheet of fabric in the form of a magnetic layer which can provide a higher magnetic therapeutic effect.
There is however a problem that a component of cobalt in the magnetic powder is susceptible to oxidation when samarium cobalt is mixed with water and glue (referred to as a binder) for ease of application or printing on the fabric sheet.
If the samarium cobalt is stored in a sealed condition, water may be deoxidized releasing hydrogen which causes explosion or steam eruption.
The samarium cobalt, Sm2Co17, is a cobalt alloy containing 20 to 25% by weight of Sm, 10 to 20% by weight of Fe, 3 to 10% by weight of Cu, and 1 to 5% by weight of Zr. The cobalt alloy has a higher magnetic characteristic but is unfavorable for being plasticized. It is common that the cobalt alloy is milled to grains of about 500 micrometers for use as a magnetic material. This increases the entire surface of the material and will accelerate the oxidation when mixed with water.
Since the samarium cobalt tends to decline the magnetic characteristic when oxidized, its oxidation will be a serious drawback to be tackled.
If oil is substituted for the water in order to prevent the oxidation, its higher viscosity may cause clogging in an application or printing device and block the mesh of a fabric sheet lowering the air permeability.
Also, the surface of each grain of the magnetic material may be covered with a film of gold. However, this will dramatically increase the overall cost while preventing the oxidation.
It is an object of the present invention, in view of the foregoing predicaments, to provide a method of making a low-cost magnetic therapeutic sheet which is less susceptible to corrosion of cobalt components.